College of Light Industry and Food Sciences, South China University of Technology , Guangzhou 510640, China.
J Agric Food Chem. 2013 Dec 11;61(49):12139-45. doi: 10.1021/jf404099y. Epub 2013 Nov 25.
Soy protein isolate (SPI) was modified by lipid peroxidation product malondialdehyde (MDA), and the in vitro digestibility of modified SPI was investigated. Results indicated that incubation with increasing MDA concentration resulted in significant carbonyl group generation and loss of free amino groups of SPI. Fluorescence loss of natural tryptophan and formation of Schiff base were observed. Noncovalent interaction between molecules was enhanced and became the main force that led to the solubility reduction of MDA-modified SPI. Differential scanning calorimetry (DSC) indicated that SPI had higher thermal stability and lower total calorimetric enthalpy after MDA pretreatment. Electrophoresis showed that β-conglycinin was more sensitive to MDA modification. In vitro digestion indicated that MDA could induce non-disulfide covalent polymer of SPI, which could not be digested by pepsin and pancreatin. β subunits of β-conglycinin became more resistant to digestion with increasing MDA concentration. Evaluation of the free amino acid profile in the digests indicated that MDA-modified SPI had deteriorating nutritive quality.
大豆分离蛋白（SPI）经脂质过氧化产物丙二醛（MDA）修饰后，研究了其体外消化率。结果表明，随着 MDA 浓度的增加，SPI 的羰基生成和游离氨基损失显著。观察到天然色氨酸荧光损失和希夫碱形成。分子间的非共价相互作用增强，成为导致 MDA 修饰 SPI 溶解度降低的主要原因。差示扫描量热法（DSC）表明，SPI 经 MDA 预处理后具有更高的热稳定性和更低的总热焓。电泳表明，β-伴大豆球蛋白对 MDA 修饰更敏感。体外消化表明，MDA 可以诱导 SPI 的非二硫键共价聚合物，这种聚合物不能被胃蛋白酶和胰蛋白酶消化。随着 MDA 浓度的增加，β-伴大豆球蛋白的β 亚基对消化的抵抗力增强。对消化物中游离氨基酸谱的评价表明，MDA 修饰的 SPI 的营养价值降低。
